A Review of IDS Processing forITRF2008 and Avenues for

Future ImprovementsF.G. Lemoine1, J.J. Valette2, G. Moreaux2, P. Willis3,4,

L. Soudarin2, P. Stepanek5, M. Otten6

1 NASA Goddard Space Flight Center, Greenbelt, Maryland, U.S.A.2 Collecte Localisation Satellites, Ramonville Saint-Agne, FRANCE3 Institut de Physique du Globe de Paris, Paris, FRANCE4 Institut Géographique National, FRANCE5 Geodetic Observatory Pecny, Ondrejov, CZECH REPUBLIC6 European Space Operations Centre, Darmstadt, GERMANY

IAG Commission 1 Symposium 2010Reference Frames for Applications in Geosciences (REFAG)

October 4-8, 2010, Marne-la-Vallée, FRANCE

OutlineI. IntroductionII. Overview of AC’s.III. Significant improvements for ITRF2008

• SRP; • Grace gravity models; • Drag parameterization.IV. Processing StandardsV. Orbit comparisonsVI. Design of Combinations.VII. Results.VIII. Lessons learned & Issues

• SPOT-5 SAA; DORIS Time-bias;IX. Future work. Analysis campaigns.

REFAG2010, Session 2, Part 2, Lemoine et al.,IDS Processing for ITRF2008 …” 3

DORIS Ground Network

Colocations: GPS (~37); SLR(9); VLBI(7); Tide gauges (~23)

Ground ties (< 3 mm): GPS-DORIS, ~25; DORIS-DORIS; ~45

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IDS Analysis Centers Participating in ITRF2008

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Preparations and ImprovementsImplemented for IDS ITRF2008 Processing (1)

Needed new a priori for ITRF2008 processingDPOD2005 (Willis et al., Adv. Space Res., 44, 535-544, 2009)• Extend ITRF2005 for POD/Altimetry applications.• Fix anomalies: e.g. Arequipa.• Specify periods when data should be deleted (station anomalies).• Test on TOPEX/Poseidon & Jason 1.• Verify with available GPS & DORIS data.

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Preparations and ImprovementsImplemented for IDS ITRF2008 Processing (2)

Solar Radiation PressureModelling Improvements (Gobinddass et al., J. Geodesy,83, 849-855, 2009)

• SRP Mismodelling impactsparticularly TZ geocenter at beta-prime (draconitic) period (~120 daysTP; ~annual for SPOT/Envisat).• Mismodelling generates“extraneous” signal in stationcoordinates at those frequencies.• Solution: Tune Cr (ReflectivityCoefficient) & Hold Fixed.

• Alternate solution: (Le Bail et al.,Adv. Space Res., 2010). Tune specificparameters of macromodel.

(Fig 5 & 8 from Gobinddass et al., 2009)

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Preparations and ImprovementsImplemented for IDS ITRF2008 Processing (3)

Drag Modelling Parameterization (Gobinddass et al., Adv. Space Res.,in press, 2010)

• Low-altitude DORIS satelliteaffected by atmospheric drag (esp.SPOT, Envisat, ~800 km).• Drag errors can bias poledetermination and worsen stationcoordinate estimation.• DORIS data density are sufficientto adjust Cd more frequently ( 1/hror 1/2hr) … & this reduces error.

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Processing Standards Summary (1)

Table 3a, Valette et al., 2010.

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Processing Standards Summary (2)(Nonconservative force models)

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Analysis Center Orbit Comparison& Validation Summary (SPOT5 example for 2005)

2874.574.131.39INA2 vs GSFC-10dg3123.203.621.23IGN3 vs LCA28535928356303282748

N

1.892.040.93IGN3 vs INA24.473.771.26IGN3 vs GSFC-base.5.444.441.69GOP vs IGN34.384.331.29IGN3 vs GSFC-base.5.374.681.51GOP vs GSFC-10dg3.594.331.25AUS5 vs IGN35.444.601.54AUS5 vs GOP1.262.200.36AUS5 vs GSFC-base.

Along-tr.Cross-tr.RadialSeries Compared(RMS orbit diffs., cm)

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DORIS data used in ITRF2008

• 1993 to end of 2008.• TOPEX, SPOT2, SPOT3, SPOT4, SPOT5, Envisat.• Only 1 yr of Jason 1 (one AC) due to Instability ofJason-1 DORIS USO.• No Jason-2 (Launched in June 2008) since PODmodelling was not validated before submissions had tobe completed.

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ITRF2008 results (1)

Valette et al., 2010.

Solar Flux

IDS-1 Horizontal Residuals

IDS-3 Horizontal Residuals

After 2 AC’s reprocesseddata with more frequent cd

parameterization

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Definition of the IDS Combination

• Gobinddass et al. (2009) improved geocenter modelling by tuning & fixing Cr coefficient foreach satellite.• Analyzed the geocenter & scale time series of each AC contribution and looked at the 365-day and 118-day signals.• This information used to define which AC’s contribute to Combination geocenter & scale.

Valette et al., 2010

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IDS-3 Geocenter & Scale(wrt ITRF2005)

Solar cycle signal?

Discontinuities inscale related tosatellites entering orleaving solution?

Valette et al., 2010

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DORIS system time-bias (wrt. SLR)(SLR/DORIS vs DORIS-only Orbit Differences)

TOPEX Envisat

Le Bail et al. 2010.But what to do for the SPOT satellites?

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SPOT-5 Anomaly?

ZTD DORIS-GNSS “Double differences”(ΔZTD2) between average valueof the SPOT-2,4, Envisat individual solutions and the SPOT-5 solution.

Stepanek et al. 2010.

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Nonconservative Force Model Improvements?

All AC’s used DTM94or MSIS86. Use neweratmosphere models?(e.g. GRACE-derived;or JB2006, Bowman et al.,

2008-J. Atmos. Sp. Physics)

Self-shadowing as in Mazarico etal., 2009, J. Spacecraft Rockets, forMRO?

Spacecraft attitude at three different orbitalSpacecraft attitude at three different orbitalpositions - view from different directions.positions - view from different directions.

UCL models for SPOT’s &Cryosat-2?

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Recent Jason-2 POD Results

DORIS data vs. Elevation

New Jason-2 DGXX Receiverdelivers at least 2X data ofprevious receivers.

High-elevation SLRResiduals for differentorbits

Zelensky et al. 2010.

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Preliminary combinations with (esa04) &without (esa03) Jason2

Valette & Moreaux, IDS AWG Darmstadt, May 2010.

Higher stability &better centering ofTZ

Summary1. The IDS for the first time constructed an technique-level combination

based on analysis by seven independent analysis centers (5 separatesoftware packages).

2. Our goals in the near future are - integrating new satellites into thesolutions (Jason2 & Cryosat2) - and developing a routine weeklycombination.

3. Issues that need to be investigated: (1) time biases on DORIS data;(2) improved non-conservative force modelling for DORIS satellites;(3) better troposphere modelling including mapping functions; (4)SPOT-5 Anomaly.

4. DORIS workshop is scheduled in Lisbon, Portugal in conjunction withJason SWT meeting (October 18-22, 2010).

5. For more details see DORIS special issue in Adv. Space Research,2010 (two volumes).

6. For more information see URL http://ids-doris.org

(some) References Willis, P., Fagard, H., Ferrage, P., Lemoine, F.G., Noll, C.E; et al., (2010). The International DORIS Service, Toward maturity, Adv. Space Research, 45(12),1408-1420, DOI: 10.1016/j.asr.2009.11.018. <====== NEW IDS CITATION.

Fagard, H. (2006), Twenty years of evolution for the DORIS permanent network: from itsinitial deployment to its renovation, J. Geodesy, 80(8-11), 429-456, DOI: 10.1007/s00190-006-0084-2.

Gobinddass, M.L.; Willis, P.; Sibthorpe, A.J.; et al. (2009). Improving DORIS geocenter time series using anempirical rescaling of solar radiation pressure models, Adv. Space Res., 44(11), 1279-1287, DOI:10.1016/j.asr.2009.08.004.

Le Bail, K., Lemoine, F.G., Chinn, D.S., (2010) GSFC contribution to ITRF2008 (2010), Adv. Space Res.,45(12), 1481-1499, DOI: 10.1016/j.asr.2010.01.03.

Stepanek, P., Dousa, J., Filler, V., Hugentobler, U. (2010), DORIS data analysis at Geodetic ObservatoryPecny using single-satellite and multi-satellite geodetic solutions, Adv. Space Research, in press, DOI:10.1016/j.asr.2010.04.015.

Valette, J.J., Lemoine, F.G., Ferrage, P., Yaya, P.; Altamimi, Z., Willis, P., Soudarin, L., (2010), IDScontribution to ITRF2008, Adv. Space Research, in press, DOI: 10.1016/j.asr.2010.05.029.

Zelensky, N.P.; Lemoine, F.G.; Ziebart, M.; et al. (2010), DORIS/ SLR POD Modeling Improvements forJason-1 and Jason-2, Adv. Space Research, in press, DOI: 10.1016/j.asr.2010.05.008

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Satellite Status & Future MissionsCRYOSAT-2 (ESA) 717 km, 92° DGXX+SLR

(launched April 2010. Data now available from IDS data centers).ENVISAT (ESA) 800 km, 98.5° D2G +SLR

(17 km orbit reduction planned in Oct. 2010).

SARAL/ALTIKA (ISRO/CNES) 880 km, 98.5° DGXX+SLR(Launch: January 2011)

HY2A (CNSA) 963 km, 99.3° DGXX+SLR+GPS(Launch: June 2011; Then HY2B, HY2C ….)

SENTINAL 3A (GMES) 814 km, 98.6° DGXX+SLR+GPS(Launch: April 2013)

JASON-3 1336 km, 66° DGXX+SLR+GPS (NOAA/EUMETSAT/CNES/NASA)

(Summer 2013; Follow-on to TOPEX, Jason-1, Jason-2)SWOT (NASA/CNES) 970 km, 78° DGXX+SLR+GPS

(Surface Water Ocean Topography; Launch 2018)